Efficient control information transmission method and apparatus for supporting multiple antenna transmission technique

ABSTRACT

The present invention relates to a wireless communication system and provides an efficient control information transmission method and apparatus for supporting a multiple antenna transmission technique. A method is provided for transmitting downlink hybrid automatic repeat request (HARQ) information related to an uplink multiple codeword transmission and includes receiving the uplink multiple codeword transmission, generating HARQ information related to each of the multiple codewords based on a result of decoding each of the multiple codewords, modulating the HARQ information, and transmitting the modulated HARQ information via one or more physical HARQ indicator channels (PHICHs).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 13,508,032,filed on May 3, 2012, currently pending, which is the National Stagefiling under 35 U.S.C. 371 of International Application No.PCT/KR2010/007871, filed on Nov. 9, 2010, which claims the benefit ofearlier filing date and right of priority to Korean Application No.10-2010-0110816, filed on Nov. 9, 2010, and also claims the benefit ofU.S. Provisional Application Ser. No. 61/259,618, filed on Nov. 9, 2009,the contents of which are all incorporated by reference herein in theirentireties.

DESCRIPTION Technical Field

The present invention relates to a wireless communication system, andmore particularly, to a method and apparatus for transmitting efficientcontrol information in order to support a multiple antenna transmissiontechnique.

Related Art

A Multiple Input Multiple Output (MIMO) scheme refers to a scheme forimproving data transmission/reception efficiency using multipletransmission antennas and multiple reception antennas, unlike a schemeusing one transmission antenna and one reception antenna. That is, atransmitter or a receiver of a wireless communication system usesmultiple antennas so as to increase capacity or improve performance. TheMIMO scheme may be called a multiple antenna technique.

In the multiple antenna transmission technique, there are a singlecodeword (SCW) scheme for simultaneously transmitting N data streamsusing one channel encoding block and a multiple codeword (MCW) schemefor transmitting N data streams using M (here, M is always equal to orless than N) channel encoding blocks. At this time, each channelencoding block generates an independent codeword and each codeword isdesigned to facilitate independent error detection.

In a system for transmitting multiple codewords, a receiver needs toinform a transmitter of success/failure of detection (decoding) of eachcodeword. Thus, the receiver may transmit a hybrid automatic repeatrequest (HARQ) ACK/NACK signal of each codeword to the transmitter.

DISCLOSURE Technical Problem

Since only a HARQ operation for transmission of an uplink singlecodeword of a user equipment (UE) having a single antenna is defined ina conventional 3GPP LTE system, there is a need for definition of a HARQoperation for transmission and retransmission of multiple uplinkcodewords of a UE having multiple antennas and a method of configuringcontrol information supporting the same.

Technical Solution

The object of the present invention can be achieved by providing amethod of transmitting downlink hybrid automatic repeat request (HARQ)information in response to uplink multiple-codeword transmission, themethod comprising receiving the uplink multiple-codeword transmission;generating HARQ information for each of the multiple-codeword based on aresult of decoding of each of the multiple-codeword; modulating the HARQinformation; and transmitting the modulated HARQ information on at leastone physical HARQ indicator channel (PHICH).

The multiple-codeword may include two-codeword transmission, the HARQinformation may be represented by 2 bits, and the modulating may beperformed using a quadrature phase shift keying (QPSK) scheme.

The HARQ information may be generated as an ACK signal if all of themultiple-codeword are decoded and may be generated as a NACK signal ifat least one of the multiple-codeword is not decoded, and the HARQinformation may be transmitted on one PHICH.

The modulated HARQ information may be transmitted on a plurality ofPHICHs and each of the plurality of PHICHs includes 1-bit HARQinformation.

In another aspect of the present invention, there is provided a methodof transmitting uplink multiple-codeword using a hybrid automatic repeatrequest (HARQ) scheme, the method including transmitting the uplinkmultiple-codeword, receiving downlink HARQ information for the uplinkmultiple-codeword transmission, and retransmitting the multiple-codewordif the HARQ information is a NACK signal, wherein the HARQ informationis generated and modulated based on a result of decoding of each of themultiple-codeword and is received on at least one physical HARQindicator channel (PHICH).

The HARQ information may include HARQ information for each of themultiple-codeword, and the retransmitting may include retransmitting, ifthe HARQ information for each of the multiple-codeword is NACK, acodeword corresponding to the HARQ information of NACK.

The HARQ information may indicate an ACK signal if all of themultiple-codeword are decoded and indicate a NACK signal if at least oneof the multiple-codeword is not decoded and the HARQ information may bereceived on one PHICH.

The retransmitting includes retransmitting all of the multiple-codewordif the HARQ information indicates the NACK signal.

The multiple-codeword transmission includes two-codeword transmission,and the retransmitting may include swapping layers to which thecodewords are mapped upon previous transmission of the two codewords andretransmitting the codewords.

In another aspect of the present invention, there is provided a basestation for transmitting downlink hybrid automatic repeat request (HARQ)information in response to uplink multiple-codeword transmission,including a reception module configured to receive an uplink signal froma user equipment (UE), a transmission module configured to transmit adownlink signal to the UE, and a processor configured to control thebase station including executing the reception module and thetransmission module, wherein the processor is configured to: receive theuplink multiple-codeword via the reception module; generate HARQinformation for each of the multiple-codeword based on a result ofdecoding of each of the multiple-codeword; modulate the HARQinformation; and transmit the modulated HARQ information on at least onephysical HARQ indicator channel (PHICH) via the transmission module.

In another aspect of the present invention, there is provided a userequipment (UE) for transmitting uplink multiple-codeword using a hybridautomatic repeat request (HARQ), including a reception module configuredto receive a downlink signal from a base station, a transmission moduleconfigured to transmit an uplink signal to the base station, and aprocessor configured to execute the transmission module and receptionmodule to transmit the uplink multiple-codeword via the transmissionmodule, receive downlink HARQ information for the uplinkmultiple-codeword transmission via the reception module and retransmitthe multiple-codeword via the transmission module if the HARQinformation is a NACK signal, and wherein the HARQ information isgenerated and modulated based on a result of decoding of each of themultiple-codeword and is received on at least one physical HARQindicator channel (PHICH).

In another aspect of the present invention, there is provided a methodof transmitting downlink control information for scheduling transmissionof uplink multiple-codeword, the method including generating downlinkcontrol information including modulation and coding scheme (MCS)information and new data indicator (NDI) information for each of themultiple-codeword as uplink scheduling information, and transmitting aphysical downlink control channel (PDCCH) including the downlink controlinformation, wherein the downlink control information further includesphysical uplink shared channel (PUSCH) resource block allocationinformation, a transmit power control (TPC) command for a scheduledPUSCH, cyclic shift information for a demodulation reference signal(DMRS), an uplink index in case of time division duplexing (TDD), adownlink allocation index in case of TDD, and channel qualityinformation (CQI) request and precoding information.

The downlink control information may further include at least one of afrequency hopping flag, a resource allocation header, a TPC command fora PUCCH, a transport block-to-codeword swap flag, a carrier indicatorand a multi-cluster flag.

Cyclic shift information for the DMRS may be given as a cyclic shiftvalue for of one layer or antenna port, and a cyclic shift value for theother layer or antenna port may be computed according to a predeterminedrule based on the cyclic shift value of the one layer or antenna port.

In another aspect of the present invention, there is provided a methodof transmitting uplink multiple-codeword scheduled by downlink controlinformation, the method including receiving downlink control informationincluding modulation and coding scheme (MCS) information and new dataindicator (NDI) information for each of the multiple-codeword as uplinkscheduling information on a physical downlink control channel (PDCCH);determining whether retransmission or not for each of the uplinkmultiple-codeword based on the NDI information; and transmitting themultiple-codeword based on scheduling information indicated by thedownlink control information, wherein the downlink control informationfurther includes physical uplink shared channel (PUSCH) resource blockallocation information, a transmit power control (TPC) command for ascheduled PUSCH, cyclic shift information for a demodulation referencesignal (DMRS), an uplink index in case of time division duplexing (TDD),a downlink allocation index in case of TDD, and channel qualityinformation (CQI) request and precoding information.

The downlink control information may further include at least one of afrequency hopping flag, a resource allocation header, a TPC command fora PUCCH, a transport block-to-codeword swap flag, a carrier indicatorand a multi-cluster flag.

Cyclic shift information for the DMRS may be given as a cyclic shiftvalue for one layer or antenna port, and a cyclic shift value for theother layer or antenna port may be computed according to a predeterminedrule based on the cyclic shift value of the one layer or antenna port.

In another aspect of the present invention, there is provided a basestation for transmitting downlink control information for schedulingtransmission of uplink multiple-codeword, including a reception moduleconfigured to receive an uplink signal from a user equipment (UE), atransmission module configured to transmit a downlink signal to the UE,and a processor configured to control the base station includingexecuting the reception module and the transmission module, wherein theprocessor is configured to generate downlink control informationincluding modulation and coding scheme (MCS) information and new dataindicator (NDI) information for each of the multiple-codeword as uplinkscheduling information and to transmit a physical downlink controlchannel (PDCCH) including the downlink control information via thetransmission module, and wherein the downlink control informationfurther includes physical uplink shared channel (PUSCH) resource blockallocation information, a transmit power control (TPC) command for ascheduled PUSCH, cyclic shift information for a demodulation referencesignal (DMRS), an uplink index in case of time division duplexing (TDD),a downlink allocation index in case of TDD, and channel qualityinformation (CQI) request and precoding information.

In another aspect of the present invention, there is provided a userequipment (UE) for transmitting uplink multiple-codeword scheduled bydownlink control information, including a reception module configured toreceive the downlink control information including modulation and codingscheme (MCS) information and new data indicator (NDI) information foreach of the multiple-codeword as uplink scheduling information on aphysical downlink control channel (PDCCH) via the reception module;determine whether retransmission or not for each of the uplinkmultiple-codeword based on the NDI information; and transmit the uplinkmultiple-codeword based on scheduling information indicated by thedownlink control information through the transmission module and aprocessor configured to execute the transmission module and receptionmodule, and wherein the downlink control information further includesphysical uplink shared channel (PUSCH) resource block allocationinformation, a transmit power control (TPC) command for a scheduledPUSCH, cyclic shift information for a demodulation reference signal(DMRS), an uplink index in case of time division duplexing (TDD), adownlink allocation index in case of TDD, and channel qualityinformation (CQI) request and precoding information.

The above general description and the following detailed description ofthe present invention are only exemplary and explain the invention ofthe claims in detail.

Advantageous Effects

According to the embodiments of the present invention, it is possible toefficiently configure control information for data retransmission intransmission of multiple uplink antennas and to provide an accurate andefficient operation for uplink data retransmission.

The effects of the present invention are not limited to theabove-described effects and other effects which are not described hereinwill become apparent to those skilled in the art from the followingdescription.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, illustrate embodiments of the inventionand together with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 is a diagram showing the structure of a downlink radio frame;

FIG. 2 is a diagram showing an example of a resource grid in onedownlink slot;

FIG. 3 is a diagram showing the structure of a downlink subframe;

FIG. 4 is a diagram showing the structure of an uplink subframe;

FIG. 5 is a diagram showing the configuration of a wirelesscommunication system having multiple antennas;

FIG. 6 is a diagram illustrating a method of transmitting and receivingmultiple uplink codewords and a method of transmitting and receivingdownlink HARQ information in response to transmission of multiple uplinkcodewords;

FIG. 7 is a diagram illustrating a method of transmitting and receivingdownlink control information for scheduling transmission of multipleuplink codewords and a method of transmitting and receiving multipleuplink codewords; and

FIG. 8 is a diagram showing the configuration of an exemplary embodimentof a base station apparatus and a user equipment (UE) according to thepresent invention.

BEST MODE

The following embodiments are proposed by combining constituentcomponents and characteristics of the present invention according to apredetermined format. The individual constituent components orcharacteristics should be considered to be optional factors on thecondition that there is no additional remark. If required, theindividual constituent components or characteristics may not be combinedwith other components or characteristics. Also, some constituentcomponents and/or characteristics may be combined to implement theembodiments of the present invention. The order of operations to bedisclosed in the embodiments of the present invention may be changed toanother. Some components or characteristics of any embodiment may alsobe included in other embodiments, or may be replaced with those of theother embodiments as necessary.

The embodiments of the present invention are disclosed on the basis of adata communication relationship between a base station and a userequipment (UE). In this case, the base station is used as a terminalnode of a network via which the base station can directly communicatewith the terminal. Specific operations to be conducted by the basestation in the present invention may also be conducted by an upper nodeof the base station as necessary.

In other words, it will be obvious to those skilled in the art thatvarious operations for enabling the base station to communicate with theterminal in a network composed of several network nodes including thebase station will be conducted by the base station or other networknodes other than the base station. The term “Base Station (BS)” may bereplaced with a fixed station, Node-B, eNode-B (eNB), or an access point(AP) as necessary. The term “relay” may be replaced with a Relay Node(RN) or a Relay Station (RS). The term “terminal” may also be replacedwith a User Equipment (UE), a Mobile Station (MS), a Mobile SubscriberStation (MSS) or a Subscriber Station (SS) as necessary. In the presentspecification, an uplink transmitter may be a UE or a relay and anuplink receiver may be a BS or a relay. Similarly, a downlinktransmitter may be a BS or a relay and a downlink receiver may be a UEor a relay. In other words, uplink transmission may mean transmissionfrom a UE to a BS, transmission from a UE to a relay, or transmissionfrom a relay to a BS. Similarly, downlink transmission may meantransmission from a BS to a UE, transmission from a BS to a relay ortransmission from a relay to a UE.

It should be noted that specific terms disclosed in the presentinvention are proposed for the convenience of description and betterunderstanding of the present invention, and the use of these specificterms may be changed to another format within the technical scope orspirit of the present invention.

In some instances, well-known structures and devices are omitted inorder to avoid obscuring the concepts of the present invention and theimportant functions of the structures and devices are shown in blockdiagram form. The same reference numbers will be used throughout thedrawings to refer to the same or like parts.

Exemplary embodiments of the present invention are supported by standarddocuments disclosed for at least one of wireless access systemsincluding an Institute of Electrical and Electronics Engineers (IEEE)802 system, a 3^(rd) Generation Project Partnership (3GPP) system, a3GPP Long Term Evolution (LTE) system, and a 3GPP2 system. Inparticular, the steps or parts, which are not described to clearlyreveal the technical idea of the present invention, in the embodimentsof the present invention may be supported by the above documents. Allterminology used herein may be supported by at least one of theabove-mentioned documents.

The following technologies can be applied to a variety of wirelessaccess technologies, for example, CDMA (Code Division Multiple Access),FDMA (Frequency Division Multiple Access), TDMA (Time Division MultipleAccess), OFDMA (Orthogonal Frequency Division Multiple Access), SC-FDMA(Single Carrier Frequency Division Multiple Access), and the like. TheCDMA may be embodied with wireless (or radio) technology such as UTRA(Universal Terrestrial Radio Access) or CDMA2000. The TDMA may beembodied with wireless (or radio) technology such as GSM (Global Systemfor Mobile communications)/GPRS (General Packet Radio Service)/EDGE(Enhanced Data Rates for GSM Evolution). The OFDMA may be embodied withwireless (or radio) technology such as Institute of Electrical andElectronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE802-20, and E-UTRA (Evolved UTRA). The UTRA is a part of the UMTS(Universal Mobile Telecommunications System). The 3GPP (3rd GenerationPartnership Project) LTE (long term evolution) is a part of the E-UMTS(Evolved UMTS), which uses E-UTRA. The 3GPP LTE employs the OFDMA indownlink and employs the SC-FDMA in uplink. The LTE—Advanced (LTE-A) isan evolved version of the 3GPP LTE. WiMAX can be explained by an IEEE802.16e (WirelessMAN-OFDMA Reference System) and an advanced IEEE802.16m (WirelessMAN-OFDMA Advanced System). For clarity, the followingdescription focuses on the 3GPP LTE and LTE-A system. However, thetechnical spirit of the present invention is not limited thereto.

Hereinafter, the structure of a downlink radio frame will be describedwith reference to FIG. 1.

In a cellular Orthogonal Frequency Division Multiplexing (OFDM) radiopacket communication system, uplink/downlink data packet transmission isperformed in subframe units. One subframe is defined as a predeterminedtime interval including a plurality of OFDM symbols. The 3GPP LTEstandard supports a type 1 radio frame structure applicable to FrequencyDivision Duplex (FDD) and a type 2 radio frame structure applicable toTime division duplexing (TDD).

FIG. 1 is a diagram showing the structure of the type 1 radio frame. Adownlink radio frame includes 10 subframes, and one subframe includestwo slots in a time domain. A time required to transmit one subframe isdefined in a Transmission Time Interval (TTI). For example, one subframemay have a length of 1 ms and one slot may have a length of 0.5 ms. Oneslot may include a plurality of OFDM symbols in a time domain andinclude a plurality of Resource Blocks (RBs) in a frequency domain.Since the 3GPP LTE system uses OFDMA in downlink, an OFDM symbolindicates one symbol duration. The OFDM symbol may be called a SC-FDMAsymbol or a symbol duration. A RB is a resource allocation unit andincludes a plurality of contiguous carriers in one slot.

The number of OFDM symbols included in one slot may be changed accordingto the configuration of a Cyclic Prefix (CP). The CP includes anextended CP and a normal CP. For example, if the OFDM symbols areconfigured by the normal CP, the number of OFDM symbols included in oneslot may be seven. If the OFDM symbols are configured by the extendedCP, the length of one OFDM symbol is increased, the number of OFDMsymbols included in one slot is less than that of the case of the normalCP. In case of the extended CP, for example, the number of OFDM symbolsincluded in one slot may be six. If a channel state is instable, forexample, if a User Equipment (UE) moves at a high speed, the extended CPmay be used in order to further reduce interference between symbols.

In case of using the normal CP, since one slot includes seven OFDMsymbols, one subframe includes 14 OFDM symbols. At this time, the firsttwo or three OFDM symbols of each subframe may be allocated to aPhysical Downlink Control Channel (PDCCH) and the remaining OFDM symbolsmay be allocated to a Physical Downlink Shared Channel (PDSCH).

The structure of the radio frame is only exemplary. Accordingly, thenumber of subframes included in the radio frame, the number of slotsincluded in the subframe or the number of symbols included in the slotmay be changed in various manners.

FIG. 2 is a diagram showing an example of a resource grid in onedownlink slot. OFDM symbols are configured by the normal CP. Referringto FIG. 2, the downlink slot includes a plurality of OFDM symbols in atime domain and includes a plurality of RBs in a frequency domain.Although one downlink slot is shown as including seven OFDM symbols andone RB includes 12 subcarriers, the present invention is not limitedthereto. Each element of the resource grid is referred to as a ResourceElement (RE). For example, a RE a(k,l) is located at a k-th subcarrierand an l-th OFDM symbol. In case of the normal CP, one RB includes 12×7REs (in case of the extended CP, one RB includes 12×6 REs). Since a gapbetween subcarriers is 15 kHz, one RB includes about 180 kHz in thefrequency domain. N^(DL) denotes the number of RBs included in thedownlink slot. The value of N^(DL) is determined based on downlinktransmission bandwidth set by scheduling of a base station.

FIG. 3 is a diagram showing the structure of a downlink subframe. Amaximum of three OFDM symbols of a front portion of a first slot withinone subframe corresponds to a control region to which a control channelis allocated. The remaining OFDM symbols correspond to a data region towhich a Physical Downlink Shared Channel (PDSCH) is allocated. The basicunit of transmission becomes one subframe. That is, a PDCCH and a PDSCHare allocated to two slots. Examples of the downlink control channelsused in the 3GPP LTE system include, for example, a Physical ControlFormat Indicator Channel (PCFICH), a Physical Downlink Control Channel(PDCCH), a Physical Hybrid automatic repeat request Indicator Channel(PHICH), etc. The PCFICH is transmitted at a first OFDM symbol of asubframe, and includes information about the number of OFDM symbols usedto transmit the control channel in the subframe. The PHICH includes aHARQ ACK/NACK signal as a response of uplink transmission. The controlinformation transmitted through the PDCCH is referred to as DownlinkControl Information (DCI). The DCI includes uplink or downlinkscheduling information or an uplink transmit power control command foran arbitrary UE group. The PDCCH may include resource allocation andtransmission format of a Downlink Shared Channel (DL-SCH), resourceallocation information of an Uplink Shared Channel (UL-SCH), paginginformation of a Paging Channel (PCH), system information on the DL-SCH,resource allocation of an higher layer control message such as a RandomAccess Response (RAR) transmitted on the PDSCH, a set of transmit powercontrol commands for individual UEs in a certain UE group, transmitpower control information, activation of Voice over IP (VoIP), etc. Aplurality of PDCCHs may be transmitted within the control region. The UEmay monitor the plurality of PDCCHs. The PDCCHs are transmitted on anaggregation of one or several contiguous control channel elements(CCEs). The CCE is a logical allocation unit used to provide the PDCCHsat a coding rate based on the state of a radio channel. The CCEcorresponds to a plurality of resource element groups. The format of thePDCCH and the number of available bits are determined based on acorrelation between the number of CCEs and the coding rate provided bythe CCEs. The base station determines a PDCCH format according to a DCIto be transmitted to the UE, and attaches a Cyclic Redundancy Check(CRC) to control information. The CRC is masked with a Radio NetworkTemporary Identifier (RNTI) according to an owner or usage of the PDCCH.If the PDCCH is for a specific UE, a cell-RNTI (C-RNTI) of the UE may bemasked to the CRC. Alternatively, if the PDCCH is for a paging message,a paging indicator identifier P-RNTI) may be masked to the CRC. If thePDCCH is for system information (more specifically, a system informationblock (SIB)), a system information identifier and a system informationRNTI (SI-RNTI) may be masked to the CRC. To indicate a random accessresponse that is a response for transmission of a random access preambleof the UE, a random access-RNTI (RA-RNTI) may be masked to the CRC.

FIG. 4 is a diagram showing the structure of an uplink subframe. Theuplink subframe may be divided into a control region and a data regionin a frequency domain. A Physical Uplink Control Channel (PUCCH)including uplink control information is allocated to the control region.A Physical uplink Shared Channel (PUSCH) including user data isallocated to the data region. In order to maintain single carriercharacteristics, one UE does not simultaneously transmit the PUCCH andthe PUSCH. The PUCCH for one UE is allocated to a RB pair in a subframe.RBs belonging to the RB pair occupy different subcarriers with respectto two slots. Thus, the RB pair allocated to the PUCCH is“frequency-hopped” at a slot edge.

Carrier Aggregation

In a general radio communication system, only one carrier is mainlyconsidered even when the bandwidths of the uplink and the downlink maybe differently set. For example, a radio communication system in whichthe number of carriers configuring the uplink or the downlink is 1 andthe bandwidth of the uplink and the bandwidth of the downlink aregenerally symmetrical with respect to each other may be provided basedon a single carrier.

International Telecommunication Union (ITU) has requested candidatetechnologies of the IMT-Advanced to support an extended bandwidth, ascompared with the existing radio communication system. However, it isdifficult to allocate a frequency having a large bandwidth in the wholeworld excluding some regions. Accordingly, as technologies ofefficiently using a plurality of small bands, carrier aggregation,bandwidth aggregation or spectrum aggregation technologies of physicallyaggregating a plurality of bands in a frequency domain so as tologically obtain the same effect as the use of a large band have beendeveloped.

The carrier aggregation technology is introduced in order to increasethroughput, to prevent cost increase due to introduction of a widebandRF element, and to guarantee compatibility with the existing system. Thecarrier aggregation technology refers to technology of exchanging databetween a UE and a BS by aggregating a plurality of carriers in abandwidth unit defined in the existing radio communication system (e.g.,a 3GPP LTE Release 8 or 9 in case of a 3GPP LTE-A system). A carrier ofthe bandwidth unit defined in the existing radio communication systemmay be called a Component Carrier (CC) or a cell. Carrier aggregationtechnology using one or more cells (or CCs) may be applied to the uplinkand the downlink. For example, the carrier aggregation technology mayinclude technology of supporting a maximum system bandwidth of 100 MHzby aggregating a maximum of five CCs even when one cell (or CC) supportsa bandwidth of 5 MHz, 10 MHz or 20 MHz.

Modeling of Multi-Input Multi-Output (MIMO) System

An MIMO system improves data transmission/reception efficiency usingmultiple transmission antennas and multiple reception antennas. In theMIMO technology, a single antenna path is not used to receive a wholemessage, that is, whole data may be received by combining a plurality ofpieces of data received through a plurality of antennas.

FIG. 5 is a diagram showing the configuration of a wirelesscommunication system having multiple antennas. As shown in FIG. 5(a), ifthe number of transmission antennas is increased to N_(T) and the numberof reception antennas is increased to N_(R), a theoretical channeltransmission capacity is increased in proportion to the number ofantennas, unlike the case where a plurality of antennas is used in onlya transmitter or a receiver. Accordingly, it is possible to improve atransfer rate and to remarkably improve frequency efficiency. As thechannel transmission capacity is increased, the transfer rate may betheoretically increased by a product of a maximum transfer rate R₀ uponutilization of a single antenna and a rate increase ratio

R _(i)=min(N _(T) , N _(R))   Equation 1

For example, in an MIMO system using four transmission antennas and fourreception antennas, it is possible to theoretically acquire a transferrate which is four times that of a single antenna system. After theincrease in the theoretical capacity of the MIMO system was proved inthe mid-1990s, various technologies of substantially improving a datatransfer rate have been actively developed up to now. In addition,several technologies are already applied to the various radiocommunication standards such as the third-generation mobilecommunication and the next-generation wireless local area network (LAN).

According to the researches into the multiple antenna technology up tonow, various researches such as researches into information theoryrelated to the computation of the communication capacity of a MIMOantenna in various channel environments and multiple accessenvironments, researches into the model and the measurement of the radiochannels of the MIMO system, and researches into space-time signalprocessing technologies of improving transmission reliability andtransmission rate have been actively conducted.

The communication method of the MIMO system will be described in moredetail using mathematical modeling. In the above system, it is assumedthat N_(T) transmission antennas and N_(R) reception antennas arepresent.

In transmitted signals, if the N_(T) transmission antennas are present,the number of pieces of maximally transmittable information is N_(T).The transmitted information may be expressed as follows.

s=└s₁, s₂, . . . , s_(N) _(T) ┘^(T)   Equation 2

The transmitted information S₁, S₂, . . . , S_(N) _(T) may havedifferent transmit powers. If the respective transmit powers are P₁, P₂,. . . , P_(N) _(T) , the transmitted information with adjusted powersmay be expressed as follows.

ŝ[ŝ₁, ŝ₂, . . . , ŝ_(N) _(T) ]^(T)=[P₁s₁, P₂s₂, . . . , P_(N) _(T) s_(N)_(T) ]^(T)   Equation 3

In addition, Ŝ may be expressed using a diagonal matrix P of thetransmit powers as follows.

$\begin{matrix}{\hat{s} = {{\begin{bmatrix}P_{1} & \; & \; & 0 \\\; & P_{2} & \; & \; \\\; & \; & \ddots & \; \\0 & \; & \; & P_{N_{T}}\end{bmatrix}\begin{bmatrix}s_{1} \\s_{2} \\\vdots \\s_{N_{T}}\end{bmatrix}} = {Ps}}} & {{Equation}\mspace{14mu} 4}\end{matrix}$

Considers that the N_(T) actually transmitted signals x₁, x₂, . . . ,x_(N) _(T) are configured by applying a weight matrix W to theinformation vector Ŝ with the adjusted transmit powers. The weightmatrix W serves to appropriately distribute the transmitted informationto each antenna according to a transport channel state, etc. x₁, x₂, . .. , x_(N) _(T) may be expressed by using the vector X as follows.

$\begin{matrix}{x = {{{\begin{bmatrix}x_{1} \\x_{2} \\\vdots \\x_{i} \\\vdots \\x_{N_{T}}\end{bmatrix}\begin{bmatrix}w_{11} & w_{12} & \ldots & w_{1\; N_{T}} \\w_{21} & w_{22} & \ldots & w_{2\; N_{T}} \\\vdots & \; & \ddots & \; \\w_{i\; 1} & w_{i\; 2} & \ldots & w_{{iN}_{T}} \\\vdots & \; & \ddots & \; \\w_{N_{T}1} & w_{N_{T}2} & \; & w_{N_{T}N_{T}}\end{bmatrix}}\begin{bmatrix}{\hat{s}}_{1} \\{\hat{s}}_{2} \\\vdots \\{\hat{s}}_{j} \\\vdots \\{\hat{s}}_{N_{T}}\end{bmatrix}} = {{W\hat{s}} = {WPs}}}} & {{Equation}\mspace{14mu} 5}\end{matrix}$

where, W_(ij) denotes a weight between an i-th transmission antenna andj-th information. W is also called a precoding matrix.

The transmitted signal x may be differently processed according to twoschemes (for example, a spatial diversity scheme and a spatialmultiplexing scheme). In case of the spatial multiplexing scheme,different signals are multiplexed and the multiplexed signal istransmitted to a receiver such that elements of information vector(s)have different values. In case of the spatial diversity scheme, the samesignal is repeatedly transmitted through a plurality of channel pathssuch that elements of information vector(s) have the same value. Acombination of the spatial multiplexing scheme and the spatial diversityscheme may be considered. That is, the same signal may be, for example,transmitted through three transmission antennas according to the spatialdiversity scheme and the remaining signals may be transmitted to thereceiver using the spatial multiplexing scheme.

If the N_(R) reception antennas are present, respective received signalsy₁, y₂, . . . , y_(N) _(R) of the antennas are expressed as follows.

y=[y₁, y₂, . . . , y_(N) _(R) ]^(T)   Equation 6

If channels are modeled in the MIMO radio communication system, thechannels may be distinguished according to transmission/receptionantenna indexes. A channel from the transmission antenna j to thereception antenna i is denoted by h_(ij). In h_(ih), it is noted thatthe indexes of the reception antennas precede the indexes of thetransmission antennas in view of the order of indexes.

FIG. 5(b) is a diagram showing channels from the N_(T) transmissionantennas to the reception antenna i. The channels may be combined andexpressed in the form of a vector and a matrix. In FIG. 5(b), thechannels from the N_(T) transmission antennas to the reception antenna imay be expressed as follows.

h_(i) ^(T)=[h_(i1), h_(i2), . . . , h_(iN) _(T) ]  Equation 7

Accordingly, all the channels from the N_(T) transmission antennas tothe N_(R) reception antennas may be expressed as follows.

$\begin{matrix}{H = {\begin{bmatrix}h_{1}^{T} \\h_{2}^{T} \\\vdots \\h_{i}^{T} \\\vdots \\h_{N_{R}}^{T}\end{bmatrix} = \begin{bmatrix}h_{11} & h_{12} & \ldots & h_{1\; N_{T}} \\h_{21} & h_{22} & \ldots & h_{2\; N_{T}} \\\vdots & \; & \ddots & \; \\h_{i\; 1} & h_{i\; 2} & \ldots & h_{{iN}_{T}} \\\vdots & \; & \ddots & \; \\h_{N_{R}1} & h_{N_{R}2} & \; & h_{N_{R}N_{T}}\end{bmatrix}}} & {{Equation}\mspace{14mu} 8}\end{matrix}$

An Additive White Gaussian Noise (AWGN) is added to the actual channelsafter a channel matrix H. The AWGN n₁, n₂, . . . , n_(N) _(R) added tothe N_(T) transmission antennas may be expressed as follows.

n=[n₁, n₂, . . . , n_(N) _(R) ]^(T)   Equation 9

Through the above-described mathematical modeling, the received signalsmay be expressed as follows.

$\begin{matrix}{y = {\begin{bmatrix}y_{1} \\y_{2} \\\vdots \\y_{i} \\\vdots \\y_{N_{R}}\end{bmatrix} = {{{\begin{bmatrix}h_{11} & h_{12} & \ldots & h_{1\; N_{T}} \\h_{21} & h_{22} & \ldots & h_{2\; N_{T}} \\\vdots & \; & \ddots & \; \\h_{i\; 1} & h_{i\; 2} & \ldots & h_{{iN}_{T}} \\\vdots & \; & \ddots & \; \\h_{N_{R}1} & h_{N_{R}2} & \; & h_{N_{R}N_{T}}\end{bmatrix}\begin{bmatrix}x_{1} \\x_{2} \\\vdots \\x_{j} \\\vdots \\x_{N_{T}}\end{bmatrix}} + \begin{bmatrix}n_{1} \\n_{2} \\\vdots \\n_{i} \\\vdots \\n_{N_{R}}\end{bmatrix}} = {{Hx} + n}}}} & {{Equation}\mspace{14mu} 10}\end{matrix}$

The number of rows and columns of the channel matrix H indicating thechannel state is determined by the number of transmission and receptionantennas. The number of rows of the channel matrix H is equal to thenumber N_(R) of reception antennas and the number of columns thereof isequal to the number N_(T) of transmission antennas. That is, the channelmatrix H is an N_(R)×N_(T) matrix.

The rank of the matrix is defined by the smaller of the number of rowsor columns, which is independent from each other. Accordingly, the rankof the matrix is not greater than the number of rows or columns. Therank rank(H) of the channel matrix H is restricted as follows.

rank(H)≤min(N _(T) , N _(R))   Equation 11

In MIMO transmission, the term “rank” denotes the number of paths forindependently transmitting signals, and the term “number of layers”denotes the number of signal streams transmitted through each path. Ingeneral, since a transmitter transmits layers corresponding in number tothe number of ranks used for signal transmission, the rank has the samemeaning as the number of layers unless otherwise noted.

Hybrid Automatic Repeat Request (HARQ)

As a control method of data reception failure, the following HARQoperation may be applied. A data transmitter may transmit a new packetif an ACK signal is received from a receiver and retransmit thetransmitted packet if a NACK signal is received, after transmitting onepacket. At this time, the packet subjected to coding with forward errorcorrection (FEC) may be retransmitted. Accordingly, the data receiverreceives and decodes one packet, transmits an ACK signal if decoding issuccessfully performed, transmits a NACK signal if decoding fails, andstores the received packet in a buffer. If the data receiver receivesthe retransmitted packet due to the NACK signal, the data receiverdecodes the retransmitted packet in association with the packet storedin the buffer, thereby increasing a packet reception success rate.

The HARQ scheme may be divided into a synchronous HARQ scheme and anasynchronous HARQ scheme according to retransmission timings. In thesynchronous HARQ scheme, if initial transmission fails, subsequentretransmission is performed at a predetermined time set by a system. Forexample, if retransmission is set to be performed in every fourth timeunit after initial transmission fails, information about aretransmission time does not need to be signaled to the receiver.Accordingly, if the data transmitter receives the NACK signal, thepacket is retransmitted in every fourth time unit until the ACK signalis received. According to the asynchronous HARQ scheme, informationabout a retransmission time is separately scheduled. Accordingly, theretransmission time of the packet corresponding to the NACK signal maybe changed according to various factors such as channel state.

The HARQ scheme may be divided into an adaptive HARQ scheme and anon-adaptive HARQ scheme depending on whether the amount of resourcesused for retransmission is set according to a channel state. In thenon-adaptive scheme, a packet modulation scheme, the number of used RBs,etc., which are used upon retransmission, are set in advance uponinitial transmission. For example, if a transmitter transmits data usingeight RBs upon initial transmission, the transmitter also retransmitsdata using eight RBs even upon retransmission. In contrast, in theadaptive scheme, the packet modulation scheme, the number of used RBs,etc. may be changed according to channel state. For example, even whendata is transmitted using eight RBs upon initial transmission,retransmission may be performed using RBs of a number of less than orgreater than eight RBs according to channel state.

A synchronous HARQ scheme is applicable to uplink data transmission of aUE having a single antenna. A HARQ ACK/NACK signal for uplink datatransmission is indicated via a PHICH or a PDCCH among downlink controlchannels. The non-adaptive HARQ scheme may be performed if the PHICH isused and the adaptive HARQ scheme may be performed if the PDCCH is used.

The PHICH is used to transmit 1-bit ACK/NACK information, a bit state 0means ACK and a bit state 1 means NACK. The 1-bit information ismodulated using a binary phase shift keying (BPSK) scheme. Thenon-adaptive scheme is performed if the PHICH is used and a redundancyversion (RV) may be changed according to a predetermined pattern.

The PDCCH is a channel including control information for uplink/downlinkdata transmission. A UE may acquire uplink control information so as toperform uplink data transmission. Downlink control information (DCI) forscheduling uplink transmission may be referred to as uplink (UL) grant.Such control information may include resource allocation information, amodulation and coding scheme (MCS) level, a new data indicator (NDI),power control information, etc. The NDI has a size of 1 bit and has abit state different from a previous NDI bit state if data to betransmitted is new data. That is, the NDI value is toggled. In case ofretransmission, control information having the same bit state as the NDIbit of previous control is transmitted. That is, the NDI value is nottoggled. Since the MCS is indicated through the PDCCH, an adaptive HARQscheme is possible.

In the 3GPP LTE system, an uplink HARQ scheme is defined as asynchronous HARQ scheme and a maximum number of retransmissions isconfigured per UE. A downlink ACK/NACK signal responding to uplinktransmission/retransmission is transmitted on a PHICH. An uplink HARQoperation follows the following rule.

1) If a PDCCH indicating a C-RNTI of a UE is accurately receivedregardless of content of HARQ feedback (ACK or NACK), a UE may performan operation indicated by the PDCCH, that is, transmission orretransmission (this may be referred to as adaptive retransmission).

2) If a PDCCH indicating a C-RNTI of a UE is not detected, HARQ feedbackmay indicate a method of performing retransmission by a UE. If HARQfeedback is NACK, the UE performs non-adaptive retransmission. That is,retransmission is performed using the same uplink resources as thosepreviously used by the same HARQ process. If HARQ feedback is ACK, theUE does not perform uplink transmission/retransmission and keeps data ina HARQ buffer. In order to perform retransmission, indication through aPDCCH is required. That is, non-adaptive retransmission is notperformed.

Meanwhile a measurement gap has higher priority than HARQretransmission. That is, if HARQ retransmission collides withmeasurement gap, HARQ retransmission is not performed.

The above-described uplink HARQ operation is summarized as shown inTable 1.

TABLE 1 HARQ feedback received by PDCCH UE received by UE UE OperationACK or NACK New New transmission is performed transmission according tothe PDCCH ACK or NACK Retransmission Retransmission is performedaccording to the PDCCH (adaptive retransmission) ACK NoneTransmission/retransmission is not performed and data is kept in theHARQ buffer. The PDCCH is required to resume retransmission. NACK NoneNon-adaptive retransmission

For detailed description of the uplink HARQ operation, refer to the 3GPPLTE standard (e.g., 3GPP TS 36.300 V8.6.0).

In the conventional 3GPP LTE system (e.g., the 3GPP LTE release 8system), if a multiple antenna transmission scheme is applied to uplinksignal transmission from a UE to a BS, a peak-to-average ratio(PAPR)/cubic metric is deteriorated. Thus, a multiple antennatransmission scheme is defined only in downlink signal transmission froma BS to a UE. Application of a multiple antenna transmission scheme toan uplink signal transmitted from a UE to a BS has been discussed forincrease in transfer rate and acquisition of diversity gain, and amethod of applying a multiple antenna transmission scheme to uplinksignal transmission in the subsequent standard (e.g., 3GPP LTE-A) of the3GPP LTE system has been discussed.

In application of the multiple antenna transmission scheme to uplinksignal transmission, an uplink transmitter (e.g., a UE) may have two orfour transmission antennas. In order to reduce overhead of a controlsignal, a maximum of two codewords may be transmitted in uplink. In asystem for transmitting multiple codewords in uplink, an uplink receiver(e.g., a BS) needs to inform the uplink transmitter (e.g., a UE) ofdetection (or decoding) success/failure of the codewords. The uplinkreceiver may transmit a HARQ ACK/NACK signal of each codeword to theuplink transmitter. With respect to uplink transmission of twocodewords, a determination as to whether new data transmission orretransmission is performed depending on whether downlink HARQ feedbackreceived by the uplink transmitter is ACK or NACK may be defined asshown in Table 2.

In a non-blank operation, new data is transmitted with respect to acodeword for which ACK is received and retransmission is performed withrespect to a codeword for which NACK is received. Meanwhile, in ablanking operation, new data is transmitted with respect to twocodewords if ACK is received with respect to the two codewords, and acodeword for which ACK is received is not transmitted and a codeword forwhich NACK is received is retransmitted if ACK is received with respectto one of the two codewords and NACK is received with respect to theother of the two codewords. If NACK is received with respect to the twocodewords, the two codewords are retransmitted.

TABLE 2 First Second Operation codeword codeword (non-blanking)Operation (blanking) ACK ACK First codeword: new First codeword: newdata data transmission transmission Second codeword: Second codeword:new data new data transmission transmission ACK NACK First codeword: newFirst codeword: non- data transmission transmission/retransmissionSecond codeword: Second codeword: retransmission retransmission NACK ACKFirst codeword: First codeword: retransmission retransmission Secondcodeword: Second codeword: non- new data transmission/retransmissiontransmission NACK NACK First codeword: First codeword: retransmissionretransmission Second codeword: Second codeword: retransmissionretransmission

Hereinafter, in a HARQ operation for the above-described uplinkmulti-codeword transmission, various embodiments of the presentinvention of a method of configuring control information on a PHICH, amethod of performing retransmission by a UE which receives a PHICH and amethod of configuring downlink control information (DCI) on a PDCCH willbe described.

Method of Configuring Control Information on a PHICH for Multiple UplinkCodeword HARQ Retransmission

As described above, a HARQ scheme for uplink data transmission issynchronously performed and a PHICH including HARQ ACK/NACK controlinformation for uplink data transmission is transmitted after apredetermined time according to an uplink data transmission period. Anuplink transmitter may determine uplink data retransmission according toan ACK/NACK state indicated by the PHICH. The ACK/NACK state isrepresented by 1 bit and this information is transmitted on a PHICHafter modulation and encoding or modulation and sequence mapping.

Multiple codewords may be used for uplink data transmission. Multiplecodewords may be used for the above-described multiple antennatransmission scheme. Alternatively, multiple codewords may be used for amultiple carrier technique (or a carrier aggregation technique). In thepresent specification, multi-codeword transmission is applicable to amultiple antenna transmission scheme or a multiple carrier technique.

Since 1 bit of information is required to indicate an ACK/NACK state ofone codeword, N bits of information is required to indicate ACK/NACKstates of N codewords. For example, in a system having two codewords, atotal of 2 bits is required to indicate the ACK/NACK states of thecodewords. N-bit information may be transmitted on a PHICH using variousmethods.

In a first embodiment, ACK/NACK signals for multiple codewords may bemodulated using a modulation method having an order higher than that ofa conventional BPSK modulation method. For example, ACK/NACK signals oftwo codewords may be represented by 2 bits and 2 bits may be modulatedusing a quadrature phase shift keying (QPSK) scheme. When more bits arerequired to represent the ACK/NACK states as in transmission of two ormore codewords, a modulation scheme such as N-PSK or N-Quadratureamplitude modulation (QAM) may be utilized. If a QPSK scheme is used,points of a total of four states may be represented by 1+j, 1−j, −1−jand −1+j. Alternatively, QPSK may be represented by 1, −1, j and −j. Inthe QPSK scheme, each point may be subjected to power normalization.

In a second embodiment, ACK/NACK signals for multiple codewords may betransmitted on multiple PHICHs. Each PHICH may include 1 bit of ACK/NACKinformation of one codeword. For example, with respect to two codewords,ACK/NACK information may be transmitted on two PHICHs.

In a third embodiment, ACK/NACK signals for multiple codewords may berepresented by 1 bit on one PHICH. For example, if two codewords aresuccessfully decoded, ACK is transmitted and, if decoding of any one ofthe two codewords fails, NACK is transmitted.

Method of Performing Multiple Uplink Codeword HARQ Retransmissionaccording to PHICH

In a first embodiment, if multiple PHICHs are transmitted with respectto transmission of multiple uplink codewords, a retransmission operationaccording to an ACK/NACK state of each codeword may be defined as shownin Table 3. An uplink transmitter (e.g., a UE) performs retransmissiononly with respect to a codeword for which NACK is received and does notretransmit a codeword for which ACK is received. If ACK is received withrespect to the two codewords, the two codewords are not transmitted.

In a second embodiment, if a single PHICH is transmitted with respect totransmission of multiple uplink codewords (ACK is transmitted if twocodewords are successfully decoded and NACK is transmitted if decodingof one or more of the two codewords fails), a retransmission operationaccording to an ACK/NACK state may be defined as shown Table 4.

TABLE 3 First code- Second word codeword Uplink transmitter OperationACK ACK First codeword: non-transmission/retransmission (PDCCH isrequired to resume retransmission) Second codeword:non-transmission/retransmission (PDCCH is required to resumeretransmission ACK NACK First codeword: non-transmission/retransmission(PDCCH is required to resume retransmission) Second codeword:retransmission (non-adaptive) NACK ACK First codeword: retransmission(non-adaptive) Second codeword: non-transmission/retransmission (PDCCHis required to resume retransmission NACK NACK First codeword:retransmission (non-adaptive) Second codeword: retransmission(non-adaptive)

TABLE 4 First and second codewords Uplink transmitter Operation ACKFirst codeword: non-transmission/retransmission (PDCCH is required toresume retransmission) Second codeword: non-transmission/retransmission(PDCCH is required to resume retransmission) NACK First codeword:retransmission (non-adaptive) Second codeword: retransmission(non-adaptive)

In a third embodiment, if a single PHICH is transmitted with respect totransmission of multiple uplink codewords (ACK is transmitted if twocodewords are successfully decoded and NACK is transmitted if decodingof one or more of the two codewords fails), a retransmission operationaccording to an ACK/NACK state may be defined as shown Table 5. Theorder of layers to which two codewords are mapped may be swapped uponretransmission. For example, swapping of codeword-to-layer mapping maybe defined as shown in Table 6.

If the layers to which the codewords are mapped are swapped uponretransmission, a codeword decoding success rate can be increased. Forexample, if a first codeword is transmitted via a first layer and asecond codeword is transmitted via a second layer upon firsttransmission, the channel state of the first layer may be better thanthat of the second layer and thus the first codeword may be successfullydecoded, but decoding of the second codeword may fail. In this case, ifcodeword-to-layer mapping is not swapped upon retransmission, the secondcodeword is transmitted via the second layer having a worse channelstate and thus decoding of the second codeword may fail. In contrast, ifcodeword-to-layer mapping is swapped upon retransmission, the secondcodeword is transmitted via the first layer having a better channelstate and a decoding success rate of the second codeword can beincreased.

TABLE 5 First and second code- words Uplink transmitter Operation ACKFirst codeword: non-transmission/retransmission (PDCCH is required toresume retransmission) Second codeword: non-transmission/retransmission(PDCCH is required to resume retransmission) NACK First codeword:retransmission (non-adaptive) swapping of codeword-to-layer mappingSecond codeword: retransmission (non-adaptive) swapping ofcodeword-to-layer mapping

TABLE 6 First codeword Second codeword First transmission First layerSecond layer Second transmission Second layer First layer Thirdtransmission First layer Second layer Fourth transmission Second layerFirst layer

Method of Configuring PDCCH DCI for Multiple Uplink Codeword HARQRetransmission

In a conventional 3GPP LTE system, a single codeword is transmitted inuplink transmission and uplink scheduling information thereof may begiven via a PDCCH having DCI format 0. The existing DCI format 0 may bedefined as shown in Table 7.

TABLE 7 Format 0 Number Contents of bit Flag for format 0/format 1Adifferentiation 1 bit Hopping flag 1 bit Resource block assignment andhopping resource allocation N bits Modulation and coding scheme andredundancy version 5 bits New data indicator 1 bit TPC command forscheduled PUSCH 2 bits Cyclic shift for DMRS 3 bits UL index (for TDD) 2bits Downlink Assignment Index (for TDD) 2 bits CQI request 1 bit

In DCI format 0, a “Flag for format 0/format 1A differentiation” fieldis a field for differentiating between DCI format 0 and DCI format 1A.Since DCI format 1A is a DCI format for scheduling downlink transmissionand has the same payload size as DCI format 0, a field fordifferentiating between DCI format 0 and DCI format 1A is included whileDCI format 0 and DCI format 1A have the same format. The “Flag forformat 0/format 1A differentiation” field having a value of 0 indicatesDCI format 0 and the “Flag for format 0/format 1A differentiation” fieldhaving a value of 1 indicates DCI format 1A.

A “Hopping flag” (frequency hopping flag) field indicates whether PUSCHfrequency hopping is applied. The “Hopping flag” field having a value of0 indicates that PUSCH frequency hopping is not applied and the “Hoppingflag” field having a value of 1 indicates that PUSCH frequency hoppingis applied.

A “Resource block assignment and hopping resource allocation” fieldindicates resource block assignment information of an uplink subframedepending on whether PUSCH frequency hopping is applied.

A “Modulation and coding scheme and redundancy version” field indicatesa modulation order and a redundancy version (RV) of a PUSCH. The RVindicates information about which subpacket is retransmitted in case ofretransmission. Among 32 states represented by 5 bits, 0 to 28 may beused to indicate modulation order and 29 to 31 may be used to indicateRV indexes 1, 2 and 3.

A “New data indicator” field indicates whether uplink schedulinginformation is for new data or retransmitted data. If the value of thisfield is toggled from an NDI value of previous transmission, thisindicates that new data is transmitted and, if the value of this fieldis not toggled from an NDI value of previous transmission, thisindicates that data is retransmitted.

A “TPC command for scheduled PUSCH” field indicates a value for decidingtransmit power of PUSCH transmission.

A “Cyclic shift for DMRS” field is a cyclic shift value used to generatea sequence for a demodulation reference signal (DMRS). The DMRS is areference signal used to estimate an uplink channel per antenna port orlayer.

A “UL index (for TDD)” field may indicate a subframe index set to uplinktransmission in a specific uplink-downlink configuration if a radioframe is configured using a time division duplexing (TDD) scheme.

A “Downlink Assignment Index (for TDD)” field may indicate a totalnumber of subframes set to PDSCH transmission in a specificuplink-downlink configuration if a radio frame is configured using a TDDscheme.

A “channel quality indicator (CQI) request” field indicates a requestfor reporting a periodic channel quality information (CQI), a precodingmatrix indicator (PMI) and a rank indicator (RI) using a PUSCH. If the“CQI request” field is set to 1, a UE transmits a report for a periodicCQI, PMI and RI using a PUSCH.

Meanwhile, a PDCCH of DCI format 2 for scheduling transmission ofmultiple downlink codewords may include control information shown inTable 8.

TABLE 8 Format 2 Contents Number of bit Resource allocation header(resource 1 bit allocation type0/type 1) Resource block assignment Nbits TPC command for PUCCH 2 bits Downlink Assignment Index (for TDD) 2bits HARQ process number 3 bits(FDD), 4 bits(TDD) Transport block tocodeword swap flag 1 bit For 1^(st) codeword Modulation and codingscheme 5 bits New data indicator 1 bit Redundancy version 2 bits For2^(nd) codeword Modulation and coding scheme 5 bits New data indicator 1bit Redundancy version 2 bits Precoding information 3 bits (2 transmitantenna at eNode-B) 6 bits (4 transmit antenna at eNode-B)

In DCI format 2, a “Resource allocation header (resource allocation type0/type 1)” field having a value of 0 indicates resource allocation ofType 0 and a “Resource allocation header (resource allocation type0/type 1)” field having a value of 1 indicates resource allocation ofType 1. Resource allocation of Type 0 may indicate that resource blockgroups (RBGs) allocated to a scheduled UE are a set of contiguousphysical resource blocks (PRBs). Resource allocation of Type 1 mayindicate physical resource blocks allocated to a scheduled UE in a setof physical resource blocks of one RBG selected from a subset of apredetermined number of RBGs.

A “Resource block assignment” field indicates a resource block allocatedto a scheduled UE according to resource assignment of Type 0 or Type 1.

A “TPC command for PUCCH” field indicates a value for deciding transmitpower of PUCCH transmission.

A “Downlink Assignment Index (for TDD)” field may indicate a totalnumber of subframes set to PDSCH transmission in a specificuplink-downlink configuration if a radio frame is configured using a TDDscheme.

A “HARQ process number” field may indicate which of a plurality of HARQprocesses managed by a HARQ entity is used for transmission.

A “Transport block to codeword swap flag” field indicates a transportblock-to-codeword mapping relationship if two transport blocks areenabled. If the “Transport block to codeword swap flag” field has avalue of 0, this indicates that a transport block 1 is mapped to acodeword 0 and a transport block 2 is mapped to a codeword 1, and, ifthe “Transport block to codeword swap flag” field has a value of 1, thisindicates that a transport block 2 is mapped to a codeword 0 and atransport block 1 is mapped to a codeword 1.

In DCI format 2, a “Modulation and coding scheme” field, a “New dataindicator” field and a “redundancy version” field are defined withrespect to a first codeword and a second codeword. The “Modulation andcoding scheme” field indicates a modulation order of a PUSCH. The “Newdata indicator” field indicates whether downlink scheduling informationis new data or retransmitted data. The “Redundancy version” fieldindicates information about which subpacket is retransmitted in case ofretransmission.

A “precoding information” field may indicate a codebook index forprecoding of downlink transmission. If a BS includes two transmissionantennas, 3 bits are necessary to indicate codebook indexes of Rank 1and Rank 2 and six bits are necessary to indicate codebook indexes ofRanks 1, 2, 3 and 4.

As described above with reference to Tables 7 and 8, in the existing3GPP LTE system, DCI format 0 for transmission of a single uplinkcodeword and DCI format 2 for transmission of multiple downlinkcodewords are defined and a PDCCH DCI format for transmission ofmultiple uplink codewords is not defined.

In the present invention, examples of a new DCI format for transmissionof multiple uplink codewords (uplink grant via a PDCCH) are proposed asshown in Tables 9, 10 and 11.

Table 9 shows an example of a new DCI format used to schedule a PUSCH ina multiple antenna port transmission mode in one uplink cell (or onecomponent carrier). Although DCI “Format 0—for MIMO” is shown in Table9, a DCI format defined in Table 9 may be referred to as a format index(e.g., DCI format 4) for differentiation from the previously defined DCIformat.

A “Hopping flag” (frequency hopping flag) field may indicate whetherPUSCH frequency hopping is applied. The “Hopping flag” field may bedefined if contiguous resource assignment is applied to a PUSCH and maybe omitted if non-contiguous resource assignment is applied to a PUSCH.

TABLE 9 Format 0 - for MIMO Contents Number of bit Hopping flag 1 bitResource block assignment and hopping N bits resource allocation TPCcommand for scheduled PUSCH 2 bits Cyclic shift for DMRS 3 bits UL index(for TDD) 2 bits Downlink Assignment Index (for TDD) 2 bits CQI request1 bit Resource allocation header (resource 1 bit allocationtype0/type 1) TPC command for PUCCH 2 bits Transport block to codewordswap flag 1 bit For 1^(st) codeword Modulation and coding scheme 5 bitsNew data indicator 1 bit For 2^(nd) codeword Modulation and codingscheme 5 bits New data indicator 1 bit Precoding information 3 bits (2transmit antenna) 6 bits (4 transmit antenna)

A “Resource block assignment and hopping resource allocation” field mayindicate resource block assignment information of an uplink subframedepending on whether PUSCH frequency hopping is applied or singlecluster assignment or multiple cluster assignment is applied.

A “TPC command for scheduled PUSCH” field indicates a value for decidingtransmit power of PUSCH transmission. The “TPC command for scheduledPUSCH” field may be defined by 2 bits if an uplink transmitter (e.g., aUE)—specific transmit power control (TPC) command is given.Alternatively, if a TPC command is given with respect to each of aplurality of antennas, the “TPC command for scheduled PUSCH” field maybe defined by a bit size of 2 bits x the number of antennas. A TPCcommand may be given with respect to each of two codewords and, in thiscase, the “TPC command for scheduled PUSCH” field may be defined by asize of 4 bits.

A “Cyclic shift for DMRS” field is a cyclic shift value used to generatea sequence for a demodulation reference signal (DMRS). The “Cyclic shiftfor DMRS” field may include an orthogonal cover code (OCC) index used toadditionally generate a DMRS. A cyclic shift value of one layer (or oneantenna port) may be given by the “Cyclic shift for DMRS” field. Acyclic shift value of another layer (or another antenna port) may becomputed from the cyclic shift value given according to a predeterminedrule based on the above layer (or antenna port).

A “UL index (for TDD)” field may indicate a subframe index set to uplinktransmission in a specific uplink-downlink configuration if a radioframe is configured using a time division duplexing (TDD) scheme.

A “Downlink Assignment Index (for TDD)” field may indicate a totalnumber of subframes set to PDSCH transmission in a specificuplink-downlink configuration if a radio frame is configured using a TDDscheme.

A “channel quality information (CQI) request” field indicates a requestfor reporting a periodic CQI, a precoding matrix indicator (PMI) and arank indicator (RI) using a PUSCH.

A “Resource allocation header (resource allocation type 0/type 1)” fieldmay indicate resource allocation of Type 0 or Type 1. Type 0 mayindicate contiguous resource allocation and Type 1 may indicate avariety of other forms of resource allocation. For example, Type 1 mayindicate non-contiguous resource allocation. If a PUSCH resourceallocation scheme is indicated via explicit or implicit signaling, the“Resource allocation header (resource allocation type 0/type 1)” fieldmay be omitted.

A “TPC command for PUCCH” field may indicate a value for decidingtransmit power of PUCCH transmission and may be omitted in some cases.

A “Transport block to codeword swap flag” field indicates a transportblock-to-codeword mapping relationship if two transport blocks areenabled. If the “Transport block to codeword swap flag” field has avalue of 0, this indicates that a transport block 1 is mapped to acodeword 0 and a transport block 2 is mapped to a codeword 1, and, ifthe “Transport block to codeword swap flag” field has a value of 1, thisindicates that a transport block 2 is mapped to a codeword 0 and atransport block 1 is mapped to a codeword 1. If one of the two codewordsis disabled, the “Transport block to codeword swap flag” field isreserved. Alternatively, if transport block to codeword swapping is notsupported, the “Transport block to codeword swap flag” field may beomitted.

A “Modulation and coding scheme” and a “new data indicator” field may bedefined with respect to two codewords (or transport blocks).

A “Modulation and coding scheme” field indicates a modulation order ofeach codeword (or each transport block). Some bit states of the“Modulation and coding scheme” field may be used to indicate RVinformation of each codeword (or each transport block). The RV mayindicate information about which subpacket is retransmitted in case ofretransmission of each codeword (or each transport block).

A “New data indicator” field indicates whether uplink schedulinginformation of each codeword (or each transport block) is new data orretransmitted data. If the value of this field is toggled from an NDIvalue of previous transmission of the codeword (or the transport block),this indicates that new data is transmitted and, if the value of thisfield is not toggled from an NDI value of previous transmission of thecodeword (or the transport block), this indicates that data isretransmitted.

A “precoding information” field may indicate a codebook index forprecoding of downlink transmission. If an uplink transmitter (e.g., aUE) includes two transmission antennas, the “precoding information”field may be defined by 3 bits in order to indicate codebook indexes ofRank 1 and Rank 2 and, if an uplink transmitter (e.g., a UE) includesfour transmission antennas, the “precoding information” field may bedefined by 6 bits in order to indicate codebook indexes of Rank 1, 2, 3and 4.

Table 10 shows another example of a new DCI format used to schedule aPUSCH in a multiple antenna port transmission mode in one uplink cell(or one component carrier). Although DCI “Format 0A” is shown in Table10, a DCI format defined in Table 10 may be referred to as a formatindex (e.g., DCI format 4) for differentiation from the previouslydefined DCI format.

Among the fields defined in the DCI format of Table 10, a description ofthe same fields as those of the DCI format of Table 9 will be omittedfor clarity of description.

In the DCI format of Table 10, a “Cyclic shift for DMRS” field mayindicate a cyclic shift value used to generate a sequence for an uplinkDMRS. The “Cyclic shift for DMRS” field may include an OCC index used toadditionally generate a DMRS. By the “Cyclic shift for DMRS” field,cyclic shift values of a plurality of layers (or antenna ports) may beexplicitly given. For example, one cyclic shift value may be representedby 3 bits and the “Cyclic shift for DMRS” field may be defined by a sizeof 12 bits in order to indicate the respective cyclic shift values offour layers (or four antenna ports).

TABLE 10 Format 0A Contents Number of bit Resource allocation header(resource 1 bit allocation type0/type 1) Hopping flag 1 bit Resourceblock assignment and hopping N bits resource allocation TPC command forscheduled PUSCH 2 bits Cyclic shift for DMRS 3 bits + N(0~3) bits TPCcommand for PUCCH 2 bits Transport block to codeword swap flag 1 bit For1^(st) codeword Modulation and coding scheme 5 bits New data indicator 1bit For 2^(nd) codeword Modulation and coding scheme 5 bits New dataindicator 1 bit Precoding information 3 bits (2 transmit antenna) 6 bits(4 transmit antenna) CQI request 1 bit UL index (for TDD) 2 bitsDownlink Assignment Index (for TDD) 2 bits

The remaining fields of the DCI format of Table 10 are equal to those ofthe DCI format of Table 9.

Table 11 shows another example of a new DCI format used to schedule aPUSCH in a multiple antenna port transmission mode in one uplink cell(or one component carrier). Although DCI “Format 0B” is shown in Table11, a DCI format defined in Table 11 may be referred to as a formatindex (e.g., DCI format 4) for differentiation from the previouslydefined DCI format.

Among the fields defined in the DCI format of Table 11, a description ofthe same fields as those of the DCI format of Table 9 will be omittedfor clarity of description.

TABLE 11 Format 0B Contents Number of bit Resource allocation header(resource 1 bit allocation type0/type 1) Hopping flag 1 bit Resourceblock assignment and N bits hopping resource allocation TPC command forscheduled PUSCH 2 bits Cyclic shift for DMRS 3 bits + N(0~3) bits TPCcommand for PUCCH 2 bits New data indicator 1 bit Transport block tocodeword swap flag 1 bit Modulation and coding scheme for 1^(st)codeword 5 bits Modulation and coding scheme for 2^(nd) codeword 5 bitsPrecoding information 3 bits (2 transmit antenna) 6 bits (4 transmitantenna) CQI request 1 bit UL index (for TDD) 2 bits Downlink AssignmentIndex (for TDD) 2 bits

In the DCI format of Table 11, a “Cyclic shift for DMRS” field mayindicate a cyclic shift value used to generate a sequence for an uplinkDMRS. The “Cyclic shift for DMRS” field may include an OCC index used toadditionally generate a DMRS. By the “Cyclic shift for DMRS” field,cyclic shift values of a plurality of layers (or antenna ports) may beexplicitly given. For example, one cyclic shift value may be representedby 3 bits and the “Cyclic shift for DMRS” field may be defined by a sizeof 12 bits in order to indicate the respective cyclic shift values offour layers (or four antenna ports).

While the “New data indicator” fields of the codewords are defined inthe DCI format of Table 9 or 10, only one “New data indicator” field maybe defined with respect to two codewords in the DCI format of Table 11.That is, two codewords (or two transport blocks) are bundled to indicatewhether uplink scheduling information is for new data or retransmitteddata. If the value of this field is toggled from an NDI value ofprevious transmission, the two codewords (or two transport blocks)indicate new data transmission and, if the value of this field is nottoggled from an NDI value of previous transmission, the two codewords(or two transport blocks) indicate retransmission.

The remaining fields of the DCI format of Table 11 are equal to those ofthe DCI format of Table 9.

In the DCI formats of Tables 9, 10 and 11, a “Carrier Indicator” fieldand a “Multi-cluster flag” field may be additionally defined. The“Carrier Indicator” field may indicate in which uplink cell (orcomponent carrier) multiple codeword PUSCH transmission is scheduled ifone or more uplink cells (or one or more component carriers) are presentand may be represented by 0 or 3 bits. The “Multi-cluster flag” fieldmay indicate whether multi-cluster allocation is applied in terms ofuplink resource allocation.

FIG. 6 is a diagram illustrating a method of transmitting and receivingmultiple uplink codewords and a method of transmitting and receivingdownlink HARQ information in response to transmission of multiple uplinkcodewords.

In step S611, a BS may receive multiple uplink codewords from a UE. StepS621 shows an operation for transmitting multiple uplink codewords atthe UE. The multiple uplink codewords may be transmitted by applying amultiple antenna technique or a multiple carrier technique to uplink.

In step S612, the BS may decode the received multiple codewords andgenerate a HARQ information (ACK/NACK) signal with respect to themultiple codewords based on the decoding result. For example, since a1-bit ACK/NACK signal may be generated with respect to each of N uplinkcodewords, a total of N bits of ACK/NACK information may be generated.

In step S613, the BS may modulate the generated HARQ information(ACK/NACK). For example, the N-bit HARQ information of the N codewordsmay be modulated according to a modulation scheme (e.g., QPSK, N-PSK,N-QAM, etc.) of a higher order. For example, 2-bit HARQ information oftwo codewords may be modulated using a QPSK scheme.

In step S614, the BS may transmit HARQ information on one or morePHICHs. For example, a total of N-bit HARQ information of the Ncodewords may be modulated using a scheme of a higher order and may betransmitted on one PHICH. Alternatively, if 1-bit HARQ information isgenerated with respect to each of the N codewords and a total of N-bitHARQ information is transmitted to the UE, 1-bit HARQ information ofeach codeword may be transmitted on one PHICH (after modulation usingthe conventional BPSK scheme) and HARQ information of multiple codewordsmay be transmitted on a total of N PHICHs. Alternatively, HARQinformation of multiple codewords may be represented by 1 bit on onePHICH. For example, if all of N codewords are successfully decoded, ACKmay be transmitted and, if decoding of only one of N codewords fails,NACK may be transmitted.

In step S622, the UE may receive HARQ information of the multiplecodewords on one or more PHICH.

In step S623, the UE may retransmit the codeword if the HARQ signal is aNACK signal. For example, if the HARQ signal includes HARQ informationof each of the multiple codewords (if HARQ information modulated to ahigher order on one PHICH is provided or if HARQ information of eachcodeword is provided on a plurality of PHICHs), the codeword, the HARQinformation of which is NACK, may be retransmitted. Alternatively, theHARQ information received on one PHICH indicates an ACK signal if all ofthe multiple codewords are decoded and indicates a NACK signal if one ormore of the multiple codewords are not decoded. If the HARQ informationindicates a NACK signal, all of the multiple codewords may beretransmitted. Alternatively, the layers to which the codewords aremapped may be swapped upon retransmission. For example, in case oftransmission of two codewords, the layers to which the codewords aremapped upon previous transmission of the two codewords may be swappedand retransmitted. That is, the layers to which the codewords are mappedmay be swapped every retransmission.

FIG. 7 is a diagram illustrating a method of transmitting and receivingdownlink control information for scheduling transmission of multipleuplink codewords and a method of transmitting and receiving multipleuplink codewords.

In step S711, a BS may generate downlink control information (DCI)including modulation and coding scheme (MCS) information and new dataindicator (NDI) information of each of multiple uplink codewords asuplink scheduling information and transmit the DCI on a PDCCH. Step S721shows an operation for receiving such DCI at a UE on the PDCCH. The DCImay further include one or more of PUSCH resource block allocationinformation, a TPC command of a scheduled PUSCH, cyclic shiftinformation for a DMRS, an uplink index in case of TDD, a downlinkallocation index in case of TDD, CQI request and precoding information,a frequency hopping flag, a resource allocation header, a TPC commandfor a PUCCH, a transport block-to-codeword swap flag, a carrierindicator and a multi-cluster flag.

In step S711, the UE may determine whether each of the uplink codewordsis retransmitted based on the DCI received on the PDCCH. Morespecifically, if the NDI included in the DCI is toggled from the NDI ofprevious transmission, new transmission may be performed and, if the NDIincluded in the DCI is not toggled from the NDI of previoustransmission, retransmission may be performed.

In step S723, the UE may transmit multiple uplink codewords based onscheduling information (resource allocation, modulation and codingscheme, etc.) indicated by the DCI. Step S712 shows an operation forreceiving the multiple uplink codewords at the BS.

The DCI for scheduling transmission of multiple uplink codewords may betransmitted on the PDCCH having the DCI format of each of Tables 9 to11.

Although the methods according to the embodiment of the presentinvention, which are performed at the BS and the UE, are described forclarity of description with reference to FIGS. 6 and 7, the abovedescription of various methods of the present invention are applicableas detailed matters and additional embodiments.

In FIGS. 6 and 7, a BS is described as an example of an uplink receiverand a relay which receives an uplink signal from a UE may perform thesame operation. Similarly, in FIGS. 6 and 7, a UE is described as anexample of an uplink transmitter and a relay which transmits an uplinksignal to a BS may perform the same operation.

FIG. 8 is a diagram showing the configuration of an exemplary embodimentof a BS apparatus and a UE (or a relay apparatus) according to thepresent invention.

In FIG. 8, a description of a BS apparatus is equally applicable to arelay apparatus as an uplink receiver and a description of a UE isequally applicable to a relay apparatus as an uplink transmitter.

Referring to FIG. 8, the BS apparatus 800 according to the presentinvention may include a reception module 810, a transmission module 820,a processor 830, a memory 840 and a plurality of antennas 850. Since theBS apparatus supports MIMO transmission/reception, the BS apparatusincludes the plurality of antennas.

The reception module 810 may receive a variety of signals, data andinformation from a UE (or a relay) in uplink (or backhaul uplink). Thetransmission module 820 may transmit a variety of signals, data andinformation to a UE (or a relay) in downlink (or backhaul downlink). Theprocessor 830 may control the overall operation of the BS apparatus 800.

The processor 830 of the BS apparatus for transmitting downlink HARQinformation of multiple uplink codewords according to an embodiment ofthe present invention may be configured to receive multiple uplinkcodewords via the reception module 810. In addition, the processor 830may be configured to generate HARQ information of each of the multiplecodewords based on the result of decoding each of the multiplecodewords. In addition, the processor 830 may be configured to modulatethe generated HARQ information and transmit the modulated HARQinformation via the transmission module 820 on one or more PHICHs.

The processor 830 of the BS apparatus for transmitting DCI forscheduling transmission of multiple uplink codewords according toanother embodiment of the present invention may be configured togenerate DCI including MCS information and NDI information of each ofthe multiple codewords as uplink scheduling information and to transmita PDCCH including the DCI via the transmission module. The DCI mayfurther include one or more of PUSCH resource block allocationinformation, a TPC command of a scheduled PUSCH, cyclic shiftinformation for a DMRS, an uplink index in case of TDD, a downlinkallocation index in case of TDD, CQI request and precoding information,a frequency hopping flag, a resource allocation header, a TPC commandfor a PUCCH, a transport block-to-codeword swap flag, a carrierindicator and a multi-cluster flag.

The above description of the methods of the present invention isapplicable as detailed matters of additional configurations of the BSapparatus.

Referring to FIG. 8, the UE 800 according to the present invention mayinclude a reception module 810, a transmission module 820, a processor830, a memory 840 and a plurality of antennas 850. Since the UE supportsMIMO transmission/reception, the UE 800 includes the plurality ofantennas.

The reception module 810 may receive a variety of signals, data andinformation from a BS (or a relay) in downlink (or backhaul downlink).The transmission module 820 may transmit a variety of signals, data andinformation to a BS (or a relay) in uplink (or backhaul uplink). Theprocessor 830 may control the overall operation of the UE 800.

The processor 830 of the UE for transmitting multiple uplink codewordsusing the HARQ scheme according to an embodiment of the presentinvention may be configured to transmit the multiple uplink codewordsvia the transmission module 820 and to receive downlink HARQ informationof transmission of multiple uplink codewords via the reception module810. In addition, the processor 830 may be configured to retransmit themultiple codewords via the transmission module if the HARQ informationis a NACK signal. In addition, the HARQ information may be generated andmodulated by the BS apparatus based on the result of decoding each ofthe multiple uplink codewords and may be received by the UE on one ormore PHICHs.

The processor 830 of the UE for transmitting multiple uplink codewordsscheduled by DCI according to another embodiment of the presentinvention may be configured to receive DCI including MCS information andNDI information of each of the multiple codewords as uplink schedulinginformation on a PDCCH via the reception module 810. The processor 830may be configured to determine whether the multiple uplink codewords areretransmitted based on the NDI information and to transmit the multipleuplink codewords based on scheduling information indicated by the DCI.The DCI may further include one or more of PUSCH resource blockallocation information, a TPC command of a scheduled PUSCH, cyclic shiftinformation for a DMRS, an uplink index in case of TDD, a downlinkallocation index in case of TDD, CQI request and precoding information,a frequency hopping flag, a resource allocation header, a TPC commandfor a PUCCH, a transport block-to-codeword swap flag, a carrierindicator and a multi-cluster flag.

The processor of the BS apparatus or the UE performs a function forprocessing information received by the BS apparatus or the UE orinformation to be externally transmitted and the memory 840 may storethe processed information for a predetermined time and may be replacedwith a component such as a buffer (not shown).

The embodiments of the present invention can be implemented by a varietyof means, for example, hardware, firmware, software, or a combination ofthem.

In the case of implementing the present invention by hardware, thepresent invention can be implemented with application specificintegrated circuits (ASICs), Digital signal processors (DSPs), digitalsignal processing devices (DSPDs), programmable logic devices (PLDs),field programmable gate arrays (FPGAs), a processor, a controller, amicrocontroller, a microprocessor, etc.

If operations or functions of the present invention are implemented byfirmware or software, the present invention can be implemented in theform of a variety of formats, for example, modules, procedures,functions, etc. The software codes may be stored in a memory unit sothat it can be driven by a processor. The memory unit is located insideor outside of the processor, so that it can communicate with theaforementioned processor via a variety of well-known parts.

The detailed description of the exemplary embodiments of the presentinvention has been given to enable those skilled in the art to implementand practice the invention. Although the invention has been describedwith reference to the exemplary embodiments, those skilled in the artwill appreciate that various modifications and variations can be made inthe present invention without departing from the spirit or scope of theinvention described in the appended claims. For example, those skilledin the art may use each construction described in the above embodimentsin combination with each other. Accordingly, the invention should not belimited to the specific embodiments described herein, but should beaccorded the broadest scope consistent with the principles and novelfeatures disclosed herein.

The aforementioned embodiments are achieved by combination of structuralelements and features of the present invention in a predeterminedmanner. Each of the structural elements or features should be consideredselectively unless specified separately. Each of the structural elementsor features may be carried out without being combined with otherstructural elements or features. Also, some structural elements and/orfeatures may be combined with one another to constitute the embodimentsof the present invention. The order of operations described in theembodiments of the present invention may be changed. Some structuralelements or features of one embodiment may be included in anotherembodiment, or may be replaced with corresponding structural elements orfeatures of another embodiment. Moreover, it will be apparent that someclaims referring to specific claims may be combined with another claimsreferring to the other claims other than the specific claims toconstitute the embodiment or add new claims by means of amendment afterthe application is filed.

INDUSTRIAL APPLICABILITY

The above-described embodiments of the present invention are applicableto various mobile communication systems.

What is claimed is:
 1. A method of transmitting downlink controlinformation (DCI) for scheduling one or more uplink codewords (CWs) by abase station (BS) in a wireless communication system supporting uplinkmultiple-input multiple-output (UL MIMO), the method comprising:generating, by the BS, DCI including modulation and coding scheme (MCS)information and new data indicator (NDI) information for each of uplinkCWs as uplink scheduling information; and transmitting, by the BS to auser equipment (UE), the DCI through a physical downlink control channel(PDCCH), wherein the DCI further includes physical uplink shared channel(PUSCH) resource block allocation information, a transmit power control(TPC) command for a scheduled PUSCH, cyclic shift information for ademodulation reference signal (DMRS), channel state information (CSI)request and precoding information, wherein the BS determines whether ornot to toggle the NDI information for each of the uplink CWs forscheduling uplink retransmission of each of the uplink CWs, wherein whena number of transmission antennas for UL MIMO is 2, the precodinginformation is configured to 3 bits indicating a codebook index from oneof a rank 1-codebook or a rank 2-codebook, and wherein when the numberof transmission antennas for UL MIMO is 4, the precoding information isconfigured to 6 bits indicating a codebook index from one of the rank1-codebook, the rank 2-codebook, a rank 3-codebook or a rank 4-codebook.2. The method according to claim 1, wherein the DCI further includes anuplink index and a downlink allocation index for time division duplexing(TDD).
 3. The method according to claim 2, wherein the NDI informationincludes first NDI information for a first uplink CW and second NDIinformation for a second uplink CW, and wherein the BS does not togglethe first NDI information if the first uplink CW was not receivedcorrectly, and the BS does not toggle the second NDI information if thesecond uplink CW was not received correctly.
 4. The method according toclaim 3, wherein the first uplink CW is retransmitted by the UE when thefirst NDI information is not toggled, and the second uplink CW isretransmitted by the UE when the second NDI information is not toggled.5. The method according to claim 4, further comprising: transmitting aphysical hybrid automatic repeat request (HARQ) indication channel(PHICH) indicating an acknowledgement (ACK) or a negativeacknowledgement (NACK), wherein the uplink retransmission of each of theuplink CWs is performed based only on the DCI regardless of the PHICH.6. The method according to claim 5, wherein each of the first NDIinformation and the second NDI information corresponds to 1-bit, andwherein each of the first NDI information and the second NDI informationis either ‘0’ or ‘1’.
 7. A method of receiving downlink controlinformation (DCI) for scheduling one or more uplink codewords (CWs) by auser equipment (UE) in a wireless communication system supporting uplinkmultiple-input multiple-output (UL MIMO), the method comprising:receiving, by the UE from a base station (BS) through a physicaldownlink control channel (PDCCH), DCI including modulation and codingscheme (MCS) information and new data indicator (NDI) information foreach of uplink CWs as uplink scheduling information; and determining, bythe UE, whether or not to retransmit each of the uplink CWs based onwhether or not the NDI information for each of the uplink CWs istoggled, wherein the DCI further includes physical uplink shared channel(PUSCH) resource block allocation information, a transmit power control(TPC) command for a scheduled PUSCH, cyclic shift information for ademodulation reference signal (DMRS), channel state information (CSI)request and precoding information, wherein when a number of transmissionantennas for UL MIMO is 2, the precoding information is configured to 3bits indicating a codebook index from one of a rank 1-codebook or a rank2-codebook, and wherein when the number of transmission antennas for ULMIMO is 4, the precoding information is configured to 6 bits indicatinga codebook index from one of the rank 1-codebook, the rank 2-codebook, arank 3-codebook or a rank 4-codebook.
 8. The method according to claim7, wherein the DCI further includes an uplink index and a downlinkallocation index for time division duplexing (TDD).
 9. The methodaccording to claim 8, wherein the NDI information includes first NDIinformation for a first uplink CW and second NDI information for asecond uplink CW, and wherein the first uplink CW is retransmitted bythe UE when the first NDI information is not toggled, and the seconduplink CW is retransmitted by the UE when the second NDI information isnot toggled
 10. The method according to claim 9, wherein uplinkretransmission of each of the uplink CWs is performed based only on theDCI regardless of a physical hybrid automatic repeat request (HARQ)indication channel (PHICH) indicating an acknowledgement (ACK) or anegative acknowledgement (NACK).
 11. A base station (BS) transmittingdownlink control information (DCI) for scheduling one or more uplinkcodewords (CWs) in a wireless communication system supporting uplinkmultiple-input multiple-output (UL MIMO), the BS comprising: a processorto generate DCI including modulation and coding scheme (MCS) informationand new data indicator (NDI) information for each of uplink CWs asuplink scheduling information; and a transmitter to transmit to a userequipment (UE) the DCI through a physical downlink control channel(PDCCH) under control of the processor, wherein the DCI further includesphysical uplink shared channel (PUSCH) resource block allocationinformation, a transmit power control (TPC) command for a scheduledPUSCH, cyclic shift information for a demodulation reference signal(DMRS), channel state information (CSI) request and precodinginformation, wherein the processor determines whether or not to togglethe NDI information for each of the uplink CWs for scheduling uplinkretransmission of each of the uplink CWs, wherein when a number oftransmission antennas for UL MIMO is 2, the precoding information isconfigured to 3 bits indicating a codebook index from one of a rank1-codebook or a rank 2-codebook, and wherein when the number oftransmission antennas for UL MIMO is 4, the precoding information isconfigured to 6 bits indicating a codebook index from one of the rank1-codebook, the rank 2-codebook, a rank 3-codebook or a rank 4-codebook.12. The BS according to claim 11, wherein the DCI further includes anuplink index and a downlink allocation index for time division duplexing(TDD).
 13. The BS according to claim 12, wherein the NDI informationincludes first NDI information for a first uplink CW and second NDIinformation for a second uplink CW, and wherein the processor does nottoggle the first NDI information if the first uplink CW was not receivedcorrectly, and the processor does not toggle the second NDI informationif the second uplink CW was not received correctly.
 14. The BS accordingto claim 13, wherein the first uplink CW is retransmitted by the UE whenthe first NDI information is not toggled, and the second uplink CW isretransmitted by the UE when the second NDI information is not toggled.15. The BS according to claim 14, wherein the transmitter transmits aphysical hybrid automatic repeat request (HARQ) indication channel(PHICH) indicating an acknowledgement (ACK) or a negativeacknowledgement (NACK), under control of the processor, and wherein theuplink retransmission of each of the uplink CWs is performed based onlyon the DCI regardless of the PHICH.
 16. The BS according to claim 15,wherein each of the first NDI information and the second NDI informationcorresponds to 1-bit, and wherein each of the first NDI information andthe second NDI information is either ‘0’ or ‘1’.
 17. A user equipment(UE) receiving downlink control information (DCI) for scheduling one ormore uplink codewords (CWs) in a wireless communication systemsupporting uplink multiple-input multiple-output (UL MIMO), the UEcomprising: a receiver; and a processor to control the receiver toreceive, from a base station (BS) through a physical downlink controlchannel (PDCCH), DCI including modulation and coding scheme (MCS)information and new data indicator (NDI) information for each of uplinkCWs as uplink scheduling information, and determine whether or not toretransmit each of the uplink CWs based on whether or not the NDIinformation for each of the uplink CWs is toggled, wherein the DCIfurther includes physical uplink shared channel (PUSCH) resource blockallocation information, a transmit power control (TPC) command for ascheduled PUSCH, cyclic shift information for a demodulation referencesignal (DMRS), channel state information (CSI) request and precodinginformation, wherein when a number of transmission antennas for UL MIMOis 2, the precoding information is configured to 3 bits indicating acodebook index from one of a rank 1-codebook or a rank 2-codebook, andwherein when the number of transmission antennas for UL MIMO is 4, theprecoding information is configured to 6 bits indicating a codebookindex from one of the rank 1-codebook, the rank 2-codebook, a rank3-codebook or a rank 4-codebook.
 18. The UE according to claim 17,wherein the DCI further includes an uplink index and a downlinkallocation index for time division duplexing (TDD).
 19. The UE accordingto claim 18, wherein the NDI information includes first NDI informationfor a first uplink CW and second NDI information for a second uplink CW,and wherein the first uplink CW is retransmitted by the UE when thefirst NDI information is not toggled, and the second uplink CW isretransmitted by the UE when the second NDI information is not toggled20. The UE according to claim 19, wherein uplink retransmission of eachof the uplink CWs is performed based only on the DCI regardless of aphysical hybrid automatic repeat request (HARQ) indication channel(PHICH) indicating an acknowledgement (ACK) or a negativeacknowledgement (NACK).